U.S. Pat. No. 3 976 577, assigned to the assignee of the present invention, shows a prior high pressure liquid filter system for industrial use in which plural side-by-side filter units are spaced along an array of vertically spaced horizontal conduits, for example backwash, filtered liquid outlet, process liquid inlet, and drain (blow off) conduits in descending order. A set of four valves, namely respective backwash, filtered liquid outlet, process liquid inlet, and drain valves, connect the respective backwash, filter liquid outlet, process liquid inlet and drain conduits to a filter unit or pair of filter units. Each of the four valves is equipped with its own individually controlled pneumatic actuator. The backwash and filtered liquid outlet valves are mechanically linked and connected to the top of the filter unit and the process liquid inlet and drain valves are mechanically linked and connected to the bottom of the filter unit. A given mechanical link assures that both of its valves are not simultaneously in the full open position and such links are mere synchronizers, actuation of the valves being by the individual pneumatic actuators. A link interconnects the pneumatic actuators for the process liquid inlet valve and drain valve and a second link interconnects the pneumatic actuators for the filter liquid outlet valve and backwash liquid inlet valve. The connections of such links to such pneumatic actuators are exposed.
In normal operation, process liquid from the process liquid inlet conduit passes up through all of the filter units simultaneously and thence appears as filtered liquid in the filtered liquid outlet. Eventually back pressure in the filter units rises due to build up on the filter of solids filtered from the process liquid. This is cured by shifting the valves connecting one or a pair of the filter units to terminate process liquid flow (filtering flow) therethrough and instead permit backwash liquid flow from the backwash conduit through the filter unit to the drain conduit while the rest of the filter units continue filtering flow. In this way the filtering operation of the system as a whole is continuous and yet the filter units are backwashed one or a pair at a time.
Filter systems of this kind are usable for filtering of various process liquids including hot and/or abrasive process liquids. For example, systems of this kind are usable in chemical plants, pulp mills, refineries etc.
In one particular example, process liquid temperatures in the range of 400.degree.-550.degree. F. are frequently encountered in refinery installations. To avoid loss of process liquid heat and to reduce the need to reheat process liquid, it is known to locate a heat retaining (insulative) box around the major portion of the filter system, the four pneumatic actuators per filter unit, or filter unit pair, being outside the heat retaining box to avoid heat damage to their internal seals.
In the prior patent, each of the actuators was controlled by a solenoid valve, the solenoid valves being located outside the heat retaining box along a bottom frame member of the apparatus.
The system disclosed in above mentioned U.S. Pat. No. 3,976,577 has proven satisfactory in service, but a continuing effort to improve systems of this general kind has resulted in the present invention.
The objects of the present invention include provision of:
(1) a filter assembly in which there is a substantial reduction in the number of pneumatic actuators as well as a change in the type of pneumatic actuator, in which there is only one actuator per filter unit (or filter unit pair) rather than one per valve, and wherein all four valves (backwash, filtered liquid output, process liquid input and drain valves) are positively mechanically interlinked for both (1) positive mechanical actuation of each and (2) simultaneous synchronization of opening and closing of all four valves, wherein the number of valve actuating parts susceptible to wear or damage is reduced by a factor of four wherein the likelihood of down time due to failed actuators is correspondingly reduced, and wherein the number of pressurizable air lines leading to actuators is correspondingly reduced so as to reduce clutter and complexity and cost in the air circuitry;
(2) an assembly as aforesaid, in which the valve actuator levers and their pivot connections to links are protected in which the drive motor is supported on actuator housings fixed to ones of the valves and not on the filter units, conduits or frame supporting the latter, wherein the motor and actuator housings are installable as a unit and are substitutable on existing field installations for actuators of earlier type, and wherein tolerance and alignment problems that may result from variations in location of the filter units, valves, conduits and frame members with respect to each other are minimized;
(3) an assembly as aforesaid, in which the number of pneumatic lines susceptible to damage is substantially reduced, and in which pilot valves previously located on the lower portion of the frame are now located to be less susceptible to damage;
(4) an assembly as aforesaid, wherein pivotable valve actuating levers are enclosed to more readily avoid contact with persons or objects moving therepast;
(5) an assembly as aforesaid, in which any tendency for the motor driven actuator to twist its housing, upon actuation by said motor, is minimized;
(6) an assembly as aforesaid, which is usable with liquids containing abrasive particles in which a tendency for abrasive particles to collect on and prematurely wear the drain valve seat is minimized.
(7) an assembly as aforesaid, which is usable with hot liquids wherein a temperature drop across the drain valve is minimized, so as to minimize temperature differential induced dimensional changes and distortions and thereby avoid valve malfunction or failure resulting therefrom; and
(8) an assembly as aforesaid, in which the major portions of the apparatus are enclosable in a heat insulating box with the drive motor and a control therefore located outside the box so as to be free of elevated temperatures within the box, the insulated box helping to reduce heat loss from preheated process liquid.
Other objects and purposes of the invention will be apparent to persons acquainted with apparatus of this type upon reading the following specification and inspecting the accompanying drawings.